1. Field of the Invention
The present invention relates to methods and apparatus for forming the tops of filled bags before the bags enter a top-sealing machine.
2. Description of the Related Art
In packaging a wide variety of materials such as pet foods and other feed-stuffs, coffee, yeast, cement, charcoal, fertilizers and other chemicals, non-rigid bags of paper or plastic conventionally are transported through one or more machines which fill the empty bags with desired amounts of materials and seal the tops of the bags after each is filled. It should be noted that "filled" merely means that each bag is loaded to a level which leaves enough bag material to be folded, closed and sealed so that the formerly open mouth of the bag is shut. As each bag is filled, the bag's walls spread apart and the bag is otherwise distorted, making it necessary to provide some means of forming the top of the bag into a flat shape which facilitates sealing in the top-sealing machine. This shape usually is obtained by tucking or gusseting the sides of the bag and bringing the front and back layers of the top together while expelling excess air remaining in the bag.
For most types of top-sealing machines, the filled bags must be presented at the entrance of the machine with the bag's top in the flat shape above-described so that the bag can be properly processed by the machine.
Several types of bag top sealing machines are in current use, including those which form heat-sealed top closures on plastic bags, taped and/or sewn top closures, and adhesive top closures. It is possible for the tops of filled bags to be shaped by hand, however, it is often more efficient to form the bag tops by machine. Examples of such bag-filling, top-forming and/or top-sealing machines are described in U.S. Pat. Nos. 2,576,471, 2,712,210, 2,925,695, 2,925,699 and 4,214,417. In general, the top-forming sections of these machines can be grouped in two classes, i.e., those which continuously grip the edges of a bag before, during and after the filling operation, and those which insert rods or fingers into the bag top and manipulate the sides and gussets of the top with shaped plates. These top-forming operations normally are carried out as the bags are continuously transported by means such as conveyor belts from the filling sections of the machines to the top-sealing sections. Nevertheless, none of these top-forming machines are capable of forming consistently shaped tops or handling filled bags which are randomly spaced on the conveyor.
Accordingly, it is an object of the present invention to provide a method and apparatus for forming a bag top which is properly shaped for sealing in a conventional top-sealing machine.
It is an additional object of the present invention to provide a method and apparatus for forming properly shaped tops on bags which are randomly positioned on means for transporting the bags through the apparatus.
It is a further object of the present invention to provide a method and apparatus for forming bag tops from which excess air has been expelled.